Photoelectric dichroism of oriented thin film CdS fabricated by pulsed-laser deposition

By means of alternating (AC) and direct (DC) photocurrent measurements, the photoelectric dichroism of thin CdS films on glass is demonstrated at 300 K. The samples are formed by pulsed-laser deposition, and defined orientations, i.e. the c-axis perpendicular (CdS⊥) or parallel (CdS∥) to the glass substrate, are achieved by variation of the laser fluence. The AC peaks of the photocurrent spectra of CdS⊥ and CdS∥ are separated by 55 meV. The absorbance spectra prove that the peak shift is caused by absorption dichroism, which is comparable with that of single crystal CdS. The separation of the DC spectra (140 meV) clearly exceeds the value of the absorption dichroism due to long-term trapping of the photocarriers at the surface of the films.